Oscillograph trace control system



ug. 3l, 1948.

A. D. SMITH,

OSCILLOGRAPH TRACE CONTROL SYSTEM Original Filed May 29. 1943 JR., El' AL 4 Sheets-Sheet l ATTMY 4 Sheets-Sheet 2 INVENTORS PCH/BMD o. swr/1J?.

Aug. 3l, 1948. A. D. SMITH, JR., ET AL OSCILLOGRAPH TRACE CONTROL SYSTEM Original Filed May 29. 1943 ATTURIWEY ug. 3l, 1948.

A. D. SMITH, J

R., ET AL 2,448,059

OSCILLOGRAPH TRACE CONTROL SYSTEM Original Filed May 29, 1943 4 Sheets-Sheet 3 BLOCK/NG WHYE GENEAH TOR TUBE INVENTORS #PCH/emo 16M/TH, Je,

HORACE M. l/rHMn/v ATTORAEY Aug. 3l, 1948. A. D. SMITH, JR., ET Al. 2,448,059

OSCILLOGRAPH TRACE CONTROL SYSTEM Original Filed May 29, 1943 4 Sheets-Sheet 4 sam/FE INVENTORS ATTORNEY Patented Aug. 31, 1948 UNITED STATES PATENT OFFICE OSCILLOGRAPH TRACE CONTROL SYSTEM Original application May 29, 1943, Serial No. 488,976. Divided and this application May 21, 1945, Serial No. 594,863

13 Claims. 1

This invention relates to cathode ray oscillographs and more particularly to scanning and deec'tion circuits for such oscillographs.

This is a division of our copending application for Radio detection sys-tem, Serial No. 488,976, filed May 26, 1943.

It is one of the objects of our present invention `to provide a method and means in connection with a cathode ray oscill-ograph to produce on the screen of the oscillograph trace lines resembling a four si-ded gure.

Another object of our invention is to provide a method and means for producing on the screen of an oscillograph two spaced apart tracings on which signals are indicated by deflectng the traclngs 'in opposite directions.

Another object of our invention is to provide a scanning circuit for cathode ray oscillographs for use in radio 'detecting systems and other electrical circuits by which the focusing and other adjustment indications such as required for determination of elevation, azimuth and range -of a detected obstacle are easily observed and compared with a high'degree of accuracy.

Still another object of the invention is to provide a scanning circuit for cathode ray oscillographs capable of providing at least two spaced apart tra-ce lines of predetermined character by which corresponding pulsations on the lines may be easily compared as -to alignment and amplitude.

The above and yother objects of the invention will become more apparent from ythe following `detailed description and the appended claims read in connection with the accompanying drawings, in which:

Fig. 1 is `a schematic block diagram of a radio detection system embodying one form -of this invention;

Fig. 2 is a schema-tic wiring diagramof a Dart of the scanning circuit for the oscillograph shown in Fig. 1;

Fig. 3 is a block diagram of another part of the scanning circuit of the oscill-ograph together with graphical illustrations of the scanning potential and deflecting pulsations applied to one of the deflection circuits of the oscillograph;

Fig. 4 is a schematic illustration of the oscillograph screen with a four sided tracing in which the opposed pulsations, while shown in alignment indicating accurately the range of the obstacle producing the pulsations, are of different amplitude and therefore indicate that the system is fimproperly directed at the obstacle producing the puls ations Fig. 5 is a block diagram of a modified portion of `the scanning circuit for the system shown in Fig. 1;

Fig. 5 is a graphical illustration of the operating steps of the elements of Fig. 5; and

Figs. 7 and 8 are schematic illustrations of an oscillograph provided with tracings in -accordance with the scanning fea-tures of Figs. 5 and 6.

Referring -to Fig. 1, one form of the cathode ray oscillograph circuits of this invention is shown in operative relation in a radio detection system which is shown to include a transmitter IU having an antenna I2 which is arranged to transmit a train of impulses such as the ser-ies XI, X2, X3, X4, etc. indicated by curve I5 (Fig. 1) in accordance with the operation of a synchronizer I4. Reradiating obstacles such as a metallic aircraft I'I within the range of the system will reflect the impulses as echo pulses EXI, EX-2, etc. curve I5. These echo pulses are received on antenna elements A2 I, '22, 23 and 24 of a directional antenna 20. The directional antenna 2G may comprise any suitable arrangement of elements where the radiation lobes are dispos-ed two in a vertical plane, such as represented by fthe positioning of antenna elements 2'I and 22, and two in a horizontal plane, such as represented by the positioning of elements 23 and 24.

The angular posi-tion of the antenna is controlled in elevation by a motor 26, and in azimuth by a motor `2'I. The motor 26 is controlled manually by a motor control device having a manually adjustable control 3I. The adjustment of the motor and therefore the angular position of the antenna '2U in elevation is indicated by a suitable dial and index device as shown at 32. The angle of adjustment of the antenna 20 for -azimuth is likewise performed rby a control device 34 for the motor 2'I. The contro1 34 has a manually adjustable control 35 and an indicating dia-l 3B.

The energy received by antenna elements 2| and 22 is transmitted over leads 4I and 42 to an alternate blocking or switch device 45. The energy received by antennas 23 and 24 is likewise transmitted over leads 43 and 44 to a second blocking or switching device 46. The devices 45 and 46, which may be of any known type of electron switch, are synchronized with the transmission of impulses by the synchronizer I4. The blocking devices operate to pass alternately the energy received by the two antennas connected therewith. That is to say, the antenna 2l is connected for reception through the device 45 of an impulse XI (curve I5) and echo pulses such as pulse EXI received in response to impulse XI, and then is blocked during the interval of reception for the next succeeding impulse X2 and corresponding trailing echo pulses. The impulse X2 and its echo pulses received by the antenna element 22 during the interval that reception by antenna 2l is blocked are now passed by the device 45. This alternate blocking then repeats with passage of impulse X3 from antenna 2l and then impulse X4 from antenna 22, etc. The device 46 operates similarly permitting passage of received energy from antennas 23 and 24. The energy passed by device 46 is represented by impulses YI, Y2, Y3, Y4, etc. and their respective echo pulses EYI, EY2, EY3, EY4, etc. (curve Ia). The corresponding impulses XI, YI; X2, Y2, etc. are in timed relation since the corresponding impulses are derived from energy of the same pulse transmitted at I2.

Following through the circuit with the pulse energy passed by the alternate blocking device 45, this energy is passed by a lead 48 to a receiver 52. The transmitted impulses XI, X2, X3, X4 etc. and their respective echo pulses received by the elevation antennas 2l and 22 are detected and amplied by the receiver 52. In curve l5, we have shown for simplication, the reception of a single echo pulse reflected by craft I'I in respense to each of the transmitted impulses.

The train of impulses and echo pulses received at the receiver 52 is applied to a pulse inverting and mixing device 53. The details of the circuit 63 which are shown in Fig. 2 will be described hereinafter. For the present, the general function of the device will be explained.

Synchronized with the transmission of impulses by connection 64 with the synchronizer I4 and passing through an adjustable delay device |05 is a square wave generator 56. The rectangular wave 51 produced by the generator 56 is applied to the device 53 and this rectangular wave is used to invert alternate pulses as indicated by wave 59 and then superimpose them on the rectangular wave 51 in the manner indicated by wave 59. The output wave 59 oi the inverting and mixing device 53 is applied to a mixing device 60.

The mixing device 60 serves to replace alternate cycles of the wave 59 with a cycle of a scanning wave 62. The wave 62 is of saw-tooth triangular form and is generated by a generator 63 synchronized through delay device I 6U by the synchronizer I4. This mixing operation is controlled by a blocking wave generator 65 which produces two rectangular waves 66 and 61 the phases of whichare 180 apart and the cycles of which are twice the duration of the cycles of the rectangular wave 59.

The mixing operation 0f the device 60 will b-e explained by reference to Fig. 3. The wave 59 is applied to a blocking tube 'I0 which is biased by the potential of wave 66. The portion 66a of the curve operates to pass energy of the wave 59 while the portion 56h operates to block the wave 59. This results in an output for the tube 'I9 corresponding to Wave 1I The waves 62 and 67 are applied to a second blocking tube I2 in a similar manner whereby an output wave 'I3 is produced in which alternate cycles of the scanning wave 62 appear. The waves 'II and 'I3 are combined by a coupling device 'I5 thereby resulting in wave 16. It will be noted that the cycles of wave I6 now comprise as alternate cycles, a cycle of the wave 59 and a cycle of wave 62.

Referring back to Fig. 1, it will be observed that the pulse energy (pulses YI, EYI, Y2,l EYZ etc. curve I5a) at the output of the blocking device 46 for antennas 23 and 24 is applied over connection 8i to a receiver 62. Similarly as in the case of receiver 52, the output of the receiver 82 is applied to a pulse inverting and mixing device 83 similar to the device 53, whereby an inversion of successive pulsation intervals s obtained (curve 58a) and the pulsations applied to a rectangular wave as indicated by curve 59a by application to the device 83 of the rectangular wave 51 from the generator 56. The wave 59a is applied with the energy of the wave 62 to a mixing device 84 identical to the device 69 to which blocking energy from generator 65 is applied. The device 84 has an output wave 76a which is similar to the wave I6 (Fig. 3) except that wave 16a is 180 out of phase therewith and the impulses appearing here are those received by the azimuth antennas 23 and 24. This phase relationship is readily observed from the aligned relationship of the two waves illustrated in Fig. 1. This diilerence in phase is obtained by reversing the wave energy 66 and 6'I from that shown in Fig. 3. That is to say, the wave 61 is used for blocking alternate cycles of the curve 59a while curve 66 is used for blocking alternate cycles of the wave 62.

The wave 'I6 is applied preferably across the vertical deecting plates 9I and 92 while the wave 76a is applied across the horizontal plates 93 and 94. The scanning portion 62a of wave 16a controls the movements of the cathode ray beam between deiecting plates 93 and 94. During the movement of the beam from the left to the right of the screen 95, the portion Sla of wave 'I6 controls the vertical deflection of the beam. Thus, the potential 62a. and 51a cause the beam to shift to point 95a and to travel therefrom as indicated by arrow 96 to 95h, thereby providing (in the absence of impluses XI, EXI etc.) a substantially straight trace between those two points. The drop in potential at the side between the first and second squares of the portion 51a causes the beam to shift instantly from points 95h to point 95e so that during the last half of the scanning potential 62a, the beam traces in the direction of arrow 9T a line between points 95o and 95d. At the end of the deflection portion 57a, the portion 62h of curve 'I6 controls the vertical scanning of the beam while portion 51h of curve 16a controls the horizontal deflection of the beam. Thus, as the potential 62h controls the scanning of the beam between the bottom and top side of the screen, the beam will be caused to first shift back to point 95e and then move as indicated by arrow 98 between points 95e and on the return movement of the beam between points 95a and 95d as indicated by arrow 99. It will be observed, therefore, that a substantially square tracing will be produced according to the wave forms of curves 'I6 and 16a.

At this point in the description, we want to make it clear that our system is not limited to a rectangular tracing but may produce in effect two trace lines spaced apart in accordance with any two of the parallel trace lines of the tracing illustrated. By this we mean that by applying the Wave 5l across the vertical plates 9| and 92 and by applying the scanning wave 62 across the horizontal plates 93 and 94, two tracings one between points 95a and 95h and the other between points 95C and 95d will be produced. This parallel tracing effect as will be clear hereinafter, may be used for producing alignment between corresponding echo pulses for the purpose of obtaining the range on the obstacle producing such echo pulses. It will also be clear that by reversing the application of the waves 51 and 62 with respect to the deiiection plates, two parallel trace lines one extending between points 95a and 95d and the other between points 95b and 95o may be obtained;

Before considering the means of determining the elevation and azimuth of a detected obstacle, the means for determining the distance to the obstacles will be described. The delay device lili! in the synchronizing circuit for the generators 63, 56 and 65 is controlled by device IDI. The control device includes a dial and indicator arrangement |82 by which the degree or retardation of energy passing through the device |50 is indicated. The device may be controlled by a hand control |63 or by means of a foot pedal |04 connected thereto by cables |05 or by any other suitable motion transmitting means. Assuming that the receivers 52 and 82 are conditioned to receive the impulses transmitted by the transmitter lll, the impulses will appear on the screen S5 as XI, X2, YS and Y4. To obtain a vzero distance indication on the device |01, `the delay device |00 is adjusted by manipulation of the control |03 until each pair of transmitter pulsations XI, X2 and YS, Y4 are brought into alignment; It is preferable to control the amplitude of the pulsations by means of amplitude controls 52a and 82a associated with receivers 52 and 82 so that the peaks thereof will extend within a centrally located circular mark I l0 on the screen S5. It will be understood that manipulation of the control |03 will cause the pulsations of each pair (Xl, X2 and Y3, YZ!) to move in opposite directions as indicated by arrows 96, 91 and 9B, S9. By proper manipulation it is possible to line up the opposed pulsations substantially as indicated. This adjustment may be taken as the zero distance position for the control. It will be understood, of course, that it is only necessary to check on the zero distance indication of the system occasionally for purposes of checking the calibration of the distance indicating dial H32.

Since each impulse is accompanied by anl echo pulse, the echo pulse EXI following the pulsation XI is to the right of X| on the screen 95 While the echo pulse EX2 is to the left of pulsation X2.

By proper manipulation of the control |03, the

pulsations X| and EXI will be shifted to the left and the pulsations X2 and EX2 will be shifted to the right until the pulsations EX! and EX2 are in alignment. The adjustment likewise shifts `the opposed pulsations EYB and EYG into alignment. When this condition is reached, the adjustment of the control as indicated on the dial |02 will give the distance to the aircraft I1. By proper adjustment of controls 52a and 82a the amplitude of the echo pulses can be increased until their tips coincide, thereby giving a more accurate setting than would be had were` they left small.

When it is desirable to obtain indications of elevation and azimuth of the aircraft or some `6 two pulsations EXI and EX2 for elevation will not be equal. Such a condition is illustrated in Fig. 4. Thus, While the pulsations EXI and EX2 will serve when in alignment as indicated in Fig. 4 for the 'ipurpose of obtaining the distance to the aircraft, sti11 1other adjustments are necessary to obtain an accurate indication of elevation and azimuth. `By proper manipulation of the control 3| for the elevation motor 2B, the antenna 2li may be maneuvered in a vertical plane until the echo pulses received by the antennas 2| and 22 'are substantially equal. When this condition is reached, the pulsations EXI and EX2 will-be substantially equal in amplitude and the peaks thereof willextend closely adjacent the center of the circular mark ||0. Such a conditionis illustrated on the screen 9-5 of Fig. 1 for the pulsa; tions XI, X2 and Y3, Y4. When this equal amplitude condition of the pulsations EXI and EX2 is obtained, the elevation indication at 32 gives the angle of elevation to the location of the air. craft I1. .I

The adjustments for azimuth are similar to the adjustments for elevation. The control 35 is ma.-l nipulated to shift the antenna 2U so as to move the 'antennas 23 and 24 in a horizontal plane until they receive equal intensity of the echo pulses. As stated in connection with the elevation adjustments, when an equal amplitude condition is reached for pulsations EY3 and lEYll, the dial in-L dication at 36 will give the angle of azimuth to the locationfof aircraft I1. The location data of distance, elevation and azimuth obtained and maintained accurate while the craft is in flight may be transmitted automatically over connections 5 to predictor mechanism for gun emplacements.

Referring back to Fig. 2, a detailed description of the pulse inverting and mixing device 53 will now be given. The train of pulses XI X2, X3 and X4 curve I5) detected by receiver 52 is applied to the input |20 to an amplifier tube V1 which acts as a4 coupling amplier for the device. The anode output `|2| reverses the pulses XI, X2, etc. to positivepulses as indicated at 22. `The pulses of curve I5 are' illustrated as negative but, of course, may be taken as positive, whichever ad'- justment is desired. Y

The energy according to the train of pulses |22 is applied to the control grid |23 of a vacuum tube V2 and to the control grid |25 of a vacuum tube Va. The tube V2 operates to invert the energy |22 applied thereto as shown at |26. This inverted energy |26 is applied to the control grid |28 of a vacuum tube V4. As will be explained hereinafter, tubes V3 and V4 operate to block out alternate sections of the energy |22 and |26, respectively.

The rectangular wave 51 produced by the generator 56 (Fig. 1) is applied to the input |30 to the control grid of a tube V5. Each cycle of the wave '51 is `formed of two rectangular portions Xa and Xb. This wave energy when obtained from the anode connection |3| of the tube V5 "is inverted as indicated at |32. This energy is passed over connection |34 to a grid of tube Vs. The portions Xb of the rectangular wave will be positive on the cathode |35 of tube Ve. This positive portion Xb is applied,V to the cathode |36 of the tube Va as a blocking potential so that alternate pulses such as the pulse X2 and the associated echo pulse EX2 are eliminated from wave |22. This leaves the anode energy of the tube Vs substantially as indicated at |40. This anode energy is applied over connection 14| to an outlet connection |42.

'The blocking potential for tube V4 is taken from the `imode connection |34 of tube V15 by a connection |44. The connection |44 applied the Wave energy '|32 to the control grid of a vacuum tube Vv. By taking the anode energy at 1| 45, it will be seen at |46 that the wave is inverted so that the portion Xa is now positive. This wave energy |46 is applied to the control grid of a. vacuum tube Vs. The portion Xa of the wave |46 is positive at the cathode |48 of the tube Vs and is applied over connection |50 to the cathode |52 of the tube V4 thereby blocking the tube V4 to those pulses occurring during the intervals covered by portions Xa of the wave |32. Since portions Xa are in phase with the portions oi the input wave I at |20 in which Xi and EX] occur, those pulses will be eliminated leaving pulses .X2 and 'EX2 as indicated at |54. The anode :output of tube V4 as indicated at |54 is applied to the outlet connection |42.

The rectangular wave |232 is also applied as `indicated at `|58 to the control grid of a `vacuum tube V9. By taking the anode potential of the tube V9. the wave |32 will be inverted back to the phase relation of the input lcurve 51 at |30. This anode energy is indicated at |59 and is applied to the output connection |42. The combining effect of the rectangular wave |59 with the pulse energies |40 and |54 produces the final output wave 59. It will new be observed that the pulses X2, X4 have been inverted with respect to the pulses Xl, X3 and the pulses XI, X2, X3 and X4 applied to the successive portions of the rectangular wave.

Referring to Figs. 5. 6, 7 an-d 8 of the drawings, We show a modication of the scanning potential for the oscillograph to be used in the system of Fig. l.. The block l|56 replaces the wave generator 56 of Fig. l. The apparatus of this block diagram is arranged to produce a wave shape diiering from the rectangular wave shape 51 by a curvature which operates during the scanning periods te deflect the tracing so as to produce in wardly or outwardly directed cusp portions, whichever may be desired as indicated in Figs. '7 and 8. The cusps of the scanning line extend the length .of the tracing thereby enabling an operator to obtain a more accurate alignment of the pulses.

The block diagram |55 includes a square wave generator |60 and an oscillator |62 which are controlled by connection E4 from the synchronizer i4. Curve a of Fig. 6 represents a rectangular wave produced by the generator |60. The oscillator |62 produces a sinusoidal wave |63 or |53a of the phase relations indicated by curves b and d of Fig. 6. When the waves of curves a and b are mixed in mixer tube |64, a wave Il substantially as indicated by curve c is produced. This wave includes alternate curved portions and |12 the cusps of which extend toward the axis |74 of the wave. When the waves of curves o; and d are mixed a wave |'l0a is produced substantially as shown by curve c.

The wave |13 or Illia, as the case maybe, is used in the system of Fig. 1 in the same manner ln which the rectangular wave .5] is used. As shown on the screen 95 in Fig. 7, the tracing |80 corresponding to wave lll) is four sided in which each side |81, |82, |83 and |84 curves inwardly toward the center of the screen. Likewise, curve |'l0a will produce a tracing |90 in which each side |9l, |92, |93 and |94 curves outwardly on A'8 the screen. By controlling the amplitude relationship of the wave i6! @curve a) and Iia (curve d), the curvature of the sides may be varied from substantially rectangular to circular and further to a, four lobe eiect. The lobe effect is indicated rslightly in Fig. 8.

While we have shown and described the principles of our invention in connection with speciiic embodiments, we recognize that various changes and modifica-tions may be made therein Without departing from the invention. For example, the crests of the oppositely curved portions of the tracings of Figs. 7 and 8 may be arranged to extend in the same direction especially where only two yspaced apart tracings are desired. The scanning intervals may also be increased with corresponding decrease in the amplitude of the deflection Wave 5l' (Fig. 1) or |5| (Fig. 6) and by proper control of the beam intensity show on the screen only the central position of each side of the tracing. It is, therefore, our aim in the appended claims to cover all such changes and' modifications as i all within the scope of our invention.

We claim:

l. A method for producing a four-sided tracing for a cathode ray oscillograph havi-ng .r-axis and y-axis deflecting elements, comprising producing two waves each having alternate cycles of scanning and trace displacement potentials, the scanning cycle of `each Wave being timed to coincide with the displacement cycle of the other, and applying one of said waves to the -axis deecting elements and the other of said waves to the y-axis deilecting elements.

2. A method according to claim 1 wherein the operation of producing said two wave forms includes the steps of producing a triangular Wave form for the scanning cycles and a substantially rectangular wave form for the displacement cycles.

3.. A method according to claim 1 wherein the operation of producing said two wave forms includes the steps of .producing a triangular wave, producing a rectangular wave having the same period as said triangular wave, and substituting for alternate cycles of one of said waves the alternate cycles of the other.

4. A method of providing a four-sided tracing for a cathode ray oscillograph having two pairs of deecting elements, comprising generating a trace displacement wave of predetermined form, producing 'in opposite phase a first and a second rectangular wave each of a period twice the period of said displacement wave, producing a scanning wave of sawtooth form having a period equal to the period of said displacement wave, applying said first rectangular wave to block alternate cycles of said displacement wave, applying said second rectangular Wave to block alternate cycles of said scanning Wave, mixing the unblocked portions of said displacement and scanning waves to produce a rst output wave having alternate cycles of the two Wave forms, applying said second rectangular wave to block alternate cycles of said displacement wave, applying said rst wave to block alternate cycles of said scanning wave, mixing the unblocked portions of the displacement wave and said scanning wave to provide a second output wave in which the corresponding cycles are out of phase with said rst output Wave, applying one of said output waves across one pair of deecting elements of the oscillograph and the other of said output waves across the other pair of deflecting elements, whereby the de.-

9 flection period of one Wave operates as a displacement potential While the scanning wave portion of the other wave operates as a scanning potential.

5. The method defined in claim 4 wherein the displacement waves are made of a given rectangular wave form, whereby the scanning operation produces substantially straight lines one for each rectangular portion of the wave.

6. The method deiined in claiin 4 wheiein the displacement wave is formed of alternate curved portions with the cusps of adjacent portions disposed inwardly toward the axis of the wave, whereby the scanning operation produces curved tracings the cusps or" which extend in opposed directions.

7. A system for producing spaced apart tracings for a cathode ray oscillograph having two pairs of opposed deflection elements, comprising means to generate a trace displacement wave of a predetermined form including a generator to produc'e a rectangular wave, an oscillator to produce a sinusoidal wave, a mixer for mixing the two waves to produce a wave having alternate curve portions with the cusps thereof extending in opposite di rections whereby the trace lines produced thereby are curved; means to generate a triangular sawtooth wave, the sawtooth wave having a period corresponding to the period of said displacement wave, means to apply said sawtooth wave across one pair of said deiiection elements, and means for applying the displacement wave across the other pair of said deection elements.

8. An oscillograph comprising -axis and y-axis delecting elements, means for producing an electron beam, means for producing two waves each having alternate cycles of scanning and deflecting potentials, the scanning cycles of each wave being timed to coincide with the deflection cycles of the other, and means for applying one of said waves to the :c-axis deflecting elements and means for applying the other of said waves to said y-axis deflecting elements.

9. An oscillograph according to claim 8 wherein the means for producing said two Waves include means for producing a triangular wave, means for producing a substantially rectangular wave and means for substituting alternate cycles of one of said Waves for the alternate cycles of the other.

10. In a cathode ray oscillograph circuit, means for providing a, triangular wave, means to provide a substantially rectangular wave having a period corresponding to the period of said triangular wave, means to block alternate cycles or said triangular and rectangular waves and means to c'ombine the resulting Waves to produce a wave having alternate cycles of said triangular wave and said rectangular wave.

11. A cathode ray oscillograph comprising two pairs of deecting elements one pair disposed along the :lr-axis and the other pair along the y-aXis, means for producing a deflection wave having two given potential values per period, means to produce in opposite phase a first and a second rectangular wave each of a period twic'e the period of the deflection wave, and means to produce a triangular wave having a period equal to the period of said deflection wave; means controlled by said i'irst rectangular wave to block alternate cycles of said deflection wave, means controlled by said second rectangular Wave to block alternate cycles of said triangular Wave, and means for mixing the unblocked portions of said deflection wave and said triangular Wave to produce a rst output wave having alternate cycles of the two wave forms; means controlled by said second rectangular wave to block alternate cycles of said deflection wave, means controlled by said rst rectangular wave to block alternate cycles of said triangular wave, and means for mixing the unblocked portions of said deflection wave and said triangular wave to provide a second output wave in which the corresponding cycles are out of phase With said first output Wave; and means for applying one of said output waves across the :i1-axis derlecting elements and means for applying the other of said output waves across said y-axis deiiecting elements.

l2. In an oscillograph circuit, means for producing a deflection Wave having two given potential values per cycle, means to produce in opposite phase a rst and a second rectangular Wave each of a period twice the period of the deection wave, means to produce a scanning Wave having a period equal to the period of said deflection wave, means controlled by said first rectangular wave to block alternate cycles of said deflection wave, means controlled by said second rectangular wave to block alternate cycles of said scanning wave, and means for mixing said unblocked portions of said scanning wave to produce an output wave having alternate cycles of the two wave forms.

13. In an oscillograph circuit, means for producing a Wave of substantially rectangular form, means to produce a sinusoidal wave form in phase with said rectangular wave form, means to mix the two wave forms to obtain a given deection wave having two spaced potential variation portions, means to produce in opposite phase a rst and a second rectangular wave each of a period twice the period of the deection wave, means to produce a scanning wave having a period equal to the period of said deection wave, means c'ontrolled by said first rectangular Wave to block alternate cycles of said deection Wave, means controlled by said second rectangular wave to block alternate cycles of said scanning wave, and means for mixing said unblocked portions of said scanning Wave to produce a first output Wave having alternate cycles of the two wave forms.

ARCHIBALD DELAP SMITH, JR. HORACE M. GUTI-IMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,077,574 Maloff Apr. 20, 1937 2,172,395 McSpadden Sept. 12, 1939 2,212,634 Buckingham Aug. 27, 1940 2,312,203 Wallace Feb. 23, 1943 2,332,881 Woerner Oct. 26, 1943 2,402,168 Lifschutz June 18, 1946 

